Agricultural harvesters, such as combines, include a head and a feeder housing which remove the crop material from the field, gather the crop material and transport the crop material to a separator in the harvester. The separator removes the grain crop material from the non-grain crop material. The grain is cleaned and deposited in a grain tank on the harvester. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle.
A trend in agricultural machines is for the size of the machines to become larger, reducing the number of passes required to cover a field. As the harvester width is increased, more grain is harvested during each pass over the field. Accordingly, it is desirable to increase the grain tank capacity to maximize productive crop harvesting time between unloading events. In many situations it is necessary to stop the harvester for unloading. Accordingly, it is desirable to reduce the frequency of unloading and to increase unloading efficiency to minimize the time required for unloading, and thereby maximize harvesting efficiency.
One apparatus for increasing the unloading rate is to provide high-speed endless-belt conveyors at an outlet of the grain tank to carry the grain into an unloading conveyor and thence into the grain cart or truck traveling alongside the vehicle. An example of this apparatus can be seen in U.S. patent application Ser. No. 12/173,583, which is assigned to Deere & Co., the assignee of the present patent application.
In the '583 application, a combine arrangement is shown in which a grain tank empties onto a cross conveyor to a door disposed to receive grain from the grain tank and to convey it to an unloading conveyor located at the side of the vehicle. In this arrangement, the door can be closed when the conveyor is not unloading, and opened for transferring grain to the cross conveyor and unloading.
In the '583 application, the door extends the entire width of the grain tank. When it opens, grain pours over the entire width onto the cross conveyor. If the cross conveyor is operating when the door is slightly opened, only a small amount of grain falls onto the cross conveyor and is carried away to the unloading conveyor. On the other hand, if the door is opened when the cross conveyor is not operating, the entire cavity in which the cross conveyor is disposed fills with grain. This applies significant downward pressure on the cross conveyor, which is transferred them to the substrate which supports the endless belt of the cross conveyor. This weight produces significant friction between the endless belt and the substrate which supports it, which can prevent the endless belt from being operated or can apply an excessive load to the cross conveyor and cross conveyor drive motor. In a similar fashion, if the unloading conveyor is not emptied upon shutdown, the grain remaining on the endless belt or auger of the unloading conveyor can cause excessive loads on the unloading conveyor drive motor on startup.
What is needed, therefore, is an unloading system that synchronizes the door opening and closing with the conveyor operation to ensure the conveyor or conveyors are not substantially loaded with grain when they are stopped. It is an object of this invention to provide such a system.